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Former Beacon Station No 419 February 17, 1999 Stockton California Additional Subsurface Investigation Key included with the boring logs in Appendix C During drilling, groundwater was encountered between the depths of approximately 44 to 46 feet below surface grade (bsg) The drill cuttings were screened with an OVM, and four discrete samples were collected from the stockpiled cuttings, composrted at the laboratory and analyzed for gasoline-range ' hydrocarbons (Table 1) All cuttings generated during this investigation were stockpiled on and covered with visqueen sheeting until subsequent disposal by Ultramar Monitoring Well Installations ' The groundwater table has risen above the well screens in wells MW-1, MW-2, and MW-3 As requested by the SJC PHS/EHD, wells MW-7, MW-8, and MW-9 were installed to ' overlap the screened intervals of the previously installed wells with the top of the screened ' interval located above the current groundwater depth The three 10-inch dia...:+Pr soil borings (MW-7, MW-8, and MW-9) were each completed as a 4-inch ID groundwater monitoring well Each of wells MW-7, MW-8, and MW-9 was completed with 25 feet of schedule 40 polyvinyl chloride (PVC) well screen with 0 020-inch factory-machined slots ' The bottom of the screened interval of each of these three wells was approximately 66 feet bsg Blank PVC well casing was installed from the top of the screened interval at 41 feet ' bsg to the surface The annular space opposite the well screen was backfilled with 43 Monterey sand to approximately one foot above the screened interval After placing the ' filter sand, the driller surged each well with a surge block to settle the filter sand and placed additional filter sand, as needed A two-foot thick seal of bentonite was then placed above ' the filter sand and hydrated with approximately five gallons of fresh water To co€:.,lete the annular seal, grout was placed with a tremie pipe from the bentonite seal to the surface The ' top of each well casing was secured with a locking watertight expansion cap and a watertight steel traffic box set slightly above surface grade The construction details are shown on the ' corresponding boring logs in Appendix C ' The 8-inch diameter soil boring SB-9 was drilled on the southern side of the UST cavity to 86'/2 feet bsg to investigate soil at the historical low groundwater level The boring was ' 1419-12 rpt 5 HORIZON ENVIRONMENTAL INC.